This invention relates to an ink jet printhead. More particularly, the invention relates to a moving nozzle ink jet.
Most ink jet printheads of the type manufactured using micro-electro mechanical systems (MEMS) technology have been proposed in a construction using nozzle chambers formed in MEMS layers on the top of a substrate with nozzle chambers formed in the layers. Each chamber is provided with a movable paddle actuated by some form of actuator to force ink in a drop through the nozzle associated with the chamber upon receipt of an electrical signal to the actuator. Such a construction is typified by the disclosure in my International Patent Application PCT/AU99/00894.
The present invention stems from the realisation that there are advantages to be gained by dispensing with the paddles and causing ink drops to be forced from the nozzle by decreasing the size of the nozzle chamber. It has been realised that this can be achieved by causing the actuator to move the nozzle itself downwardly in the chamber thus dispensing with the paddle, simplifying construction and providing an environment which is less prone to the leakage of ink from the nozzle chamber.
According to the invention there is provided an ink jet printhead including:
a plurality of nozzles each adapted to eject drops of ink toward a surface to be printed; wherein,
each of the nozzles has an external actuator and an apertured roof portion; the roof portion defining an inner surface for contacting the ink and an opposing outer surface operatively connected to the external actuator such that the actuator moves the roof portion away from the surface to be printed to eject the ink.
Preferably, each of the nozzles further includes an associated nozzle chamber adapted to be supplied with ink via at least one conduit in an underlying substrate.
Preferably, the roof portion has a sidewall depending from its periphery to telescopically engage a peripheral sidewall extending from an opposing floor portion to define the nozzle chamber.
Preferably, the actuator comprises a bend actuator mounted on the substrate at a proximal end as a cantilever beam, and is arranged to support the roof portion of the nozzle chamber at a distal end of the cantilever beam, such that in use, actuation of the nozzle ejects ink through the apertured roof portion by moving it toward the floor portion.
Preferably, the conduit in the underlying substrate communicates with the nozzle chamber through an opening in the floor portion, the opening being sufficiently large so as not to significantly impede the flow of ink therethrough.
Preferably, ink in the nozzle chamber in use is inhibited from flowing back through the conduit upon downward movement of the roof portion, primarily by viscous drag on the walls of the conduit.